ADDUCTS OF ALKALI METALS WITH AZOBENZENE
[CONTRIBUTION FROM
T€IE UNIVERSITY OB
375
TORONTO]
Adducts of Alkali Metals with Azsbenzene J. W. B. REESOR
AND
GEORGE F WRIGHT
Received October 16, 1956 Adducts have been prepared directly from azobenzene and two atom equivalents of lithium, sodium, and potassium. In general these dimetal addhcts are less reactive than the analogous stilbene-dimetal adducts. Benzyl chloride, which couples t o diphenylethane upon treatment with stilbene-disodium adduct, gives a good yield of N,N'-dibenzyl-N,N'-diphenylhydrazine. Normal alkyl halides and methyl sulfate give only N , N '-disubstituted hydrazobenzenes but secondary and tertiary halides, and a phosphate, give N-monosubstituted hydrazobenzene. Isopropyl methanesulfonate, however, gives both mono- and disubstituted hydrazobenzenes. The monosubstituted hydrazobenzenes may be obtained from the diphenylhydrazyl metal, which is derived from equivalent amounts of the dimetal adduct and hydrazobenzene. The nature of azobenzene-monometal adducts has not been demonstrated but they are probably not free radicals.
In their comprehensive report on the addition of alkali metals to aromatic unsaturated compounds Schlenk and Bergmann' mention the reaction of azobenzene with sodium in ethyl ether to form an unidentified precipitate. They were more successful in the use of potassium phenylbiphenylethyl as a source in situ of metal; they obtained an adduct comprising 1 atom of potassium per mole of azobenzene. Later WittigZprepared N,N-'dilithiuindiphenylhydrazyl by treatment of hydrazobenzene with
manner described previously. 2,5 A characteristic color change and also magnetic susceptibility measurement have persuaded NTittig et al. that the monometal adduct system contains about 50% of the free radical I11 in mobile equilibrium with I and 11. Furthermore they postulated that the reaction product of the radical I11 and benzoyl chloride, N beiieoyl dibenzopiperazine, ITT, disproportionates into the dibenzoyl derivative, V, and I (the actual products). N- C-CoH,;
C,H5COC1
ON* IV
111
I
1-/'
dispropor-
tionation
and
methyllithium in ethyl ether. When he treated this indirectly prepared di-adduct with an equivalent of azobenzene in ethyl ether a color change occurred. The resulting system was equivalent to N-monolithium diphenylhydrazyl and was designated by Wittig as a free radical, CsHh-K-N(Li)C6H6. Thus, the direct addition of alkali metals to azobenzene was not accomplished, but several adducts from analogs were reported. A disodium adduct in ethyl ether from azomethane and from 1,lO-dimethyl dibenz~pyridazine~ was reported, and later both disodium and dilithium adducts were obtained from dibenzopyridazine I in ethyl ether.4The latter dimetal adducts I1 (M = S a or Li) were converted to monometal adducts (1:l metal and azo compound) by treatment of dibenzopyridazine in the (1) (2) (3) (4)
W. Sch!enk and E . Bergmann, Ann., 463, 1 (1928). G. T i t t i g , Angew. Chem., 53,241 (1940). C. Wittig and 0. Sticknoth, Ber., 68B, 928 (1935). G. Wittiy and -4.Schumacker, Ber., 88, 234 (1955).
N- COCcH5
By use of 2,5-dioxahexane as the reaction medium we have obtained the dimetal adducts of azobenzene with lithium, sodium, and potassium in quantitative yield. Presumably the dilithium adduct is identical with Wittig's product from hydrazobenzene and methyllithium since it gives the same alkylation derivatives. By use of a modified Schlenk tubebshaken horizontally at 25" to 30" with metal of about 3 - ~ msurface .~ a t 240 cycles per min. it has been found that addition occurs more slowly with azobenzene than with stilbene (Table I). While the differences in rate can in part be attributed to the electropositivity oi the metal and to the bond degeneracy in the unsaturated compound, the physical state of the metal surface seems to be highly important. Table I shows that use of a Waring Blendor operating at 8000 r.p.m. markedly increases the rate of adduct formation. (5) J. W.B. Reesor, J . G. Smith, and G. F Wright, J. Org. Chem., 19,940 (1954).
376
REESOR AND WRIGHT
VOL.
22
TABLE I Annr.rro\ Unsdturateci Compound I
OF
~ I E rr T ~
----_
solrltloll
Metal
._
Iriitial
W
Color Final
2,5-I)IOXiHEXANE
Ppt Color
Reaction time (hr )
-
2 -10 50 12
__ Reaction
__
VCSSPI
I
Stilbenea QmhPilLenc.
'
iizobmzcne" A7oben7ene" bobenzenea
v1'
Red IJlgllt 1ellow
1,L
1:1 K I, 1
Gr w r i I3t own
Green
R?d Red Yellow
Yellow Red Red Yellow
(i
2
-
Schlenk Same &me
Same Warine Blendor
'' (tians)
There is evidence for solvation of the alkene-dimetal adducts in the solid6 form and in solution,' but no firm decision can be made about solvation of dimetal adducts of azobenzene. However, it is notable that the color of Wittig's dilithium diphenylhydrazyl in ether is different from our azobenzene-dilithium adduct in dioxahexane, although the two organometallic compounds are evidently identical except for the solvate. If this is evidence for coordination then the bond with 2,5-dioxahexane must be strong in the yellow solid azobenzenedilithium adduct since the latter does not change color under 0.001 mm. at 40-50" for one hour.
stilbene6 in order to designate the present solutions as azobenzene-metal monoadducts. Treatment of the 1: 1 azobenzene-metal system with carbon dioxide yields an equal mixture of azobenzene and hydrazobenzene, the latter being a decarboxylation product. Essentially the same behavior occurs with benzoyl chloride as with carbon dioxide, a 60% yield of sym-dibenzoyldiphenlhydraaine being produced. These reactions might seem to designate the system as a dimetal adduct (VI, h!t = Li, K a or K) to which the extra equivalent of azobenzene is eoordinated (instead of dioxahexane) via its otherwise unshared electron pairs as the complex VII:
The characteristic color of the azobenzene-dimetal adducts affords an interesting qualitative exhibition of metal interchange. If the red azobenzene-dipotassium adduct in 2,Ei-dioxahexane is shaken for 2 days with lithium metal the color intensity decreases markedly and the appearance and reaction with water of the metallic lithium shows that it is coated with metallic potassium. The reverse reaction is apparent in the color change from yellow to orange-red when the azobenzene-dilithium adduct is shaken with potassium metal. Wittig2 reported that colorless diphenylhydrazyl dilithium (VI) in diethyl ether becomes brown when an equivalent of azobenzene is added to it. We too observe a color change when the yellow suspension of azobenzene-dilithium adduct in dioxahexane is treated with azobenzene, although the effect of the medium is apparent because the final color is different from that observed by Wittig. Our yellow suspension is dissolved to give a dark green solution. Likewise the red azobenzene-dipotassium adduct is dissolved by azobenzene in dioxahexane to give a color of much greater depth. We have not yet been able to devise experiments such as those with stilbene-dimetal adducts and
Despite evidence from reaction with carbon dioxide and benzoyl chloride it seems worthwhile to consider alternatives. It may be observed that by redistribution of electronic charge VI1 beconies VIII, analogous with a structure suggested for the alkene monometal adduct^.^ The latter also react with carbon dioxide as if they were dimetal adducts although in part they react with 2-chloropropane and triethyl phosphate t o give coupling products and polymers expected from an intermediate free radical. We have not been able l o isolate such products indicative of a transitory radical by treatment of the 1: 1 azobenzene-metal system with 2-chloropropane. But these products would be tetrazanes and diazopolymers. The complex unstable mixture that we do obtain from the 1: 1 azobenzene-metal system is not unexpected if these substances have indeed been formed. Therefore we consider the 1: 1 azobenzene-metal system to resemble VI11 (with or without coordinated ether) in equilibrium with VI and azobenzene rather than an initial radical state like 111 which was suggested by Wittig for the monometal dibenzopiperazine system. A choice between these alternatives cannot be made by paramagnetic resonance absorption studies8 because the spins in either may be expected to be uncoupled. However it
(6) B. R1. Mikhailov and IT.G. Chernova, Doklady Akad. ,Vauk, S.X.S.R., 74,939 (1950);Chem. Abstr., 45,4698 (1951). ( 7 ) A. G. Brook, H. L. Cohen, and G. F Wright, J . Orq. Chem., 18,447 (1953).
(8) D. Lipkin, D. E. Paul, J. Toiinsend, and S. I Wrissman, Science, 117,534 (1953).
APRIL
1957
377
ADDUCTS OF ALKALI MET-4LS WITH AZOBENZENE
might be expected that a system initially containing free radicals as typified by I11 ought to convert 1,3-butadiene to its polymer. This gas is inert toward the azobenzene-monolithium system during 2 hr. a t 25". In general the azobeneene-dimetal adducts, although less reactive than the stilbene-dimetal adducts, tend to form the same type of product. The lesser reactivity is not entirely disadvantageous since scission of ether molecules by the azobenzene-metal system is slight. For example the stilbenedisodium adduct attacks 2,5-dioxahexane to form 27% of diphenylethane in 8 days. By contrast the azobenzene-disodium adduct attacks 2,5dioxahexane in 55 days to form not more than 13% of h ydrasobenzene. The reactions of azobenzene-dimetal adducts are listed in Table 11. The products and the yields from dimethyl sulfate and from 1,3-dichloropropane are the same as those reported by Wittigj2thus confirming the identity of his dilithium diphenylhydrasyl with our adduct. The products and yields from n-propyl chloride, tert-butyl chloride, and 1,4-dichlorobutane are comparable with corresponding alkylations of stil-
bene-dimetal adducts but a notable contrast is observed with benzyl chloride. This halide reacts with the stilbene-disodium adduct yielding only diphenylethane, stilbene, and sodiuni chloride but with azobenzene the main product is sym-N,N'-dibenxylhydrazobenzene, XI. We are interpreting this difference in terms of homopolar versus heteropolar scissions within transient complex intermediates. The homopolar scission is depicted in structure IX for the reaction of benzyl chloride with stilbene-disodium adduct,
B
TABLE I1 AZOBENZENE-DIA~KALI METAL BDDUCTS AND VARIOUS REAGENTS AT A TEMPERATURE O F 0-25'
Reagent
Metal of Diadduct
No. of Moles
(Hr.)
92 96 74 74 70
7
90
4
Duration of Reaction
Methyl sulfate
Sa
0.01
0.01
n-Propyl chloride Benzyl chloride
Li Na K
0.01 0.01
0.3 0.3 5.5 5.5
Na Na
0.01 0.01
1.1 4.5
Na K Li K
3-a
0.11 0.01 0.01 0.01 0.06 0.01 0.01 0.01 0.01 0.01
Li
0.01
&Butyl chloride
Li Na
Ethylene 2,5-Dioxahexane
K Na
0.01 0.01 0.01 0.01
Iso-propyl chloride Iso-propyl bromide
Li
Isopropyl iodide
Li
K Triisopropyl phosphate Isopropyl methane sulfonate Isopropyl chloride
K K
N-Monosubstituted Hydrazobenzene ( 7cYield)
N,N'-Disubstituted Wydrazobenzene (70Yield)
-
3 12 days 30
-
2 1 1 14 days 48 Methyl sulfate added after 22 hr . 11 days ' 50 8 Methyl sulfate added after 55 days
AZObenzene ( % Recovered)
Other Products (70 Yield)
1
1
7
1,2-Diphenyl&ham 8
90
90
-
3
1
30 77 73 81 78 77 60
20
66
2
40
3
27
86 ( N , N dimethyl)
21 23 No reaction 49 (dimethyl)
25 Hydrazobenzene 26 (monomethyl)
5 Hydrazobenzene
378
REESOB AND WRIGHT
In contrast to this homopolar concerted electron redistribution is the heteropolar shift depicted in structure X for reaction of benzyl chloride with the azobenzene-dipotassium adduct in which the unshared nitrogen electron pairs may play a part.
XI
CsHs
Of course, the isolation of 8% of diphenylethane and 77, of azobenzene in the latter reaction shows that homopolar scission also must be occurring to a lesser extent. I n contrast to reactions of isopropyl halides with the stilbene-dimetal adducts (which yield both mono- and dialkylated diphenylethanes) are the slower reactions with azobenzene-dimetal adducts. From the latter only monoalkylated hydrazobenzenes (XIII) are obtained. The reaction with isopropyl chloride is particularly slow, and product yields may not be significant because of long-term contamination. However, the inertness of the system has been demonstrated by addition of methyl sulfate 22 hr. after the isopropyl chloride is introduced. The 86% yield of methyl derivative shows that the halide has not reacted appreciably. The stepwise concerted mechanism suggested6for reaction of isopropyl halides with stilbene-dimetal adducts may be applied to azobenzene-dimetal adducts. A relatively rapid alkylation a t one nitrogen is thought to be followed by a slow replacement of metal by hydrogen (8 on propyl) a t the second nitrogen atorn in the transitory XII.
VOL.
22
observed that the alkylation is noticeably exothermic only during the first half of the reaction. Moreover, 20% of dialkylation can be effected if the highly reactive isopropyl methanesulfonate is used instead of the halide. It is probable that this dialkylation is due to the strong polarization in the ester rather than to a different concerted transition that it might undergo. As Table I1 shows, triisopropyl phosphate behaves like the halides. The difference in the polarization of the first and second N-K linkages is shown also in the reaction of the azobenzene-dimetal adducts with substances containing active hydrogen. I n contrast to solvolysis of the stilbene-dimetal adducts (which has not been effected in a stepwise manner) the azobenzene-dipotassiurn adduct can he converted to N,N’-diphenylhydrazylpotassium XIV. While this conversion may be accomplished with an alcohol like 1-butanol, the resultant potassium butoxide is troublesome if, subsequently, the system is treated with an alkylating agent. Consequently hydrazobenzene is preferred as a source of active hydrogen in order to avoid wastage of the alkylating substance, C~H~--N-II
I
C&--N--K VI, where Ill = K
C~H~---NI-I --3 iI + C&-SH C6Hs-N-K 2
l
CsHs-N-H XIV
-
l ~ e z ~ 0 4CJIr--N--CII3
I
Cp,Hr,--N--H XV
Treatment of XIV with isopropyl bromide gives about the same yield of isopropylhydrazobenzene (XIII) as may be obtained directly from VI so that there is no advantage in the preparation and use of XIV for this purpose. However, dimethyl sulfate, which yields only dialkylation product from the adduct (VI), reacts with XIV to give a 26% yield of N-methylhydrazobenzene together with a 23% yield of N,N ‘-dimethylhydraxobenzene XVI. The formation of the dialkylation product indicates that TJI and hydrazobenzene are in equilibrium with Me XIV. Although the alkylation products shown in Table c,a,-N--l:-rr -3- CeT15-S-.’ TI I1 have been authenticated by analysis2 none of h1e + KBr Me them has otherwise been characterized. We have CCHs-N---C C~lIj-~--H + CHg=CIICHa chosen to establish the structure of three of the derivatives by hydrogenolysis. Using the recomXlTl mended method9 by which we obtained a 92% yield and a 46y0 conversion of hydrazobenzene to aniline we have treated N,N’-dimethylhydrazobenzene XI1 (XVI) with 137-1 Raney nickel in ethanol for 4 hr. It is apparent that this is a steric argument a t 1000 p.s.i. The yield of N-methylaniline is 52% though one may question why hindrance should not while 25% of XVI is recovered unchanged. This be less in XI1 than it is in the analogous carbon method is unsuccessful when applied to N,N’-disystem in which both mono- and dialkylation occur. phenylpyrazolidine (XVII) because the ethanol beWe attribute the difference to the greater covalence haves as a partial alkylating agent. However, the of the AT--K bond (as contrasted to the C-K bond) ( 9 ) L. W. Covert and H. Adkins, J . Am. Chem. Soc., 54, which should accentuate steric effects, It has been 4116 (1932).
I !
l 1
APRIL
1957
ADDUCTS O F ALKALI METALS WITH AZOBENZENE
alternative choice of dioxane not only gives a nearly quantitative yield of N,N'-diphenyl-l,3-propanediamine but also enables the use of milder conditions (24", atmospheric pressure, W-2 catalyst) in the medium. The hydrogenolysis of N,N'-diphenylpyridazolidine proves to be much more difficult, and the compound is recovered unchanged under conditions used for XVI and XVII. When the pressure is increased to 4500 p.s.i. and the temperature to 150160' in dioxane with W-2 catalyst hydrogenolysis is accompanied by hydrogenation and deamination. A 51% yield of N-cyclohexylpyrrolidine is obtained, corresponding with the behavior of other 1,a-diazacyclohexanes.lO-ll The authors are grateful to the Defence Research Board of Canada for generous support of this research. They acknowledge experimental aid from W. Boos and R. Kullnig. EXPERIMENTAL
A11 melting points have been corrected against reliable standards. X-ray diffraction powder patterns are reported as the strongest lines (d, 8) a t intensities (Z/11)using Cu K (Ni filtered) radiation. All petroleum ether used was alkenefree and peroxide-free, b.p. 60-70". Preparation and purification of reagents. Nitrogen, purified by passage through 3 washing towers of Brady's solution,I2 2 towers of flake sodium hydroxide and a 2 X 10 inch length of Drierite, was used to protect all liquids during preparation and reaction. Purification of 2,5-dioxahexane was effected by reflux over sodium until addition of a few crystals of benzophenone formed a stable solution of the blue ketyl. Final distillation a t 85" from this stored solution was carried out just prior to use. Alkyl halides were extracted with 80-96% sulfuric acid, washed with aqueous sodium bicarbonate, then water, and were dried with magnesium sulfate and distilled. Methyl sulfate, washed with bicarbonate solution and dried with magnesium sulfate was distilled (b.p. 76'/15 mm.). Technical azobenaene was distilled, b.p. 152-155" (11-14 mm.), then crystallized (3.4 ml./g.) a t O'C., filtered by suction and washed with cold ethanol (0.3 ml./g.). Recovery was 85%. Preparation of azobenzene dinzetal adducts. (1) The method described previouslyGwas used, all glassware being flushed with nitrogen while it was externally flamed prior to use. The Schlenk tube containing a single piece of metal in excess and 0.01 mole of azobenaene per 40 ml. of dioxahexane was shaken until reaction was complete, then wae decanted from excess metal. (2) A stainless steel 1-1. Waring Blendor (Cenco No. 17235) container was modified to include a phig cock a t the bottom and a Teflon gasket under the lid, which was equipped with ports for nitrogen influx and efflux or for sampling. This vessel was especially effective for decreasing the time of lithium addition; indeed it wax necessary to employ strong air blast cooling for preparations as large as 0.1 mole. General method for reactions of the adducts. The adduct prepared from 1.82 g. (0.01 mole) of azobenaene in 40 ml. of dioxahexane was transferred under nitrogen to a 100-ml. three-necked flask equipped with thermometer, dropping tube, and sealed stirrer. Addition of the reagent (0.022 mole) in 5 ml. of dioxahexane was carried out a t 0-5°C. (IO) A. Kataenellenbogen, Ber., 34,3828 (1901). (11) S. Racine, Ann., 239, 71 (1887). (12) L. J. Brady, Znd. Eng. Chem. ( A n a l . Ed.), 20, 1034 (1948).
379
This temperature was maintained for 30 min. subsequent to addition and was then allowed to rise to 20-25". When reaction was complete (no color change when an aliquot was exposed to air) the dioxahexane was vacuum-evaporated and the residue was dissolved in 30 ml. each of ethyl ether and water. The et,her phase was washed with water and the combined aqueous phases were then washed with ether (30 ml.). This ether phase, washed with water, was combined with the first one and then evaporated under vacuum to leave the crude reaction product. Chromatographic separation of products. (1) O n silicic acid. The crude reaction product was dissolved in a minimum of hexane and the solution was applied to a 1 X 10 cm. column of Mallinckrodt 100-mesh chromatographic silicic acid, 20'% wat.er. Elution with hexane removed combined azobenzene with mono- and dialkylated hydraaobenzenes. Subsequently hydraaobenzene could be eluted by a 95 :5 hexane-methanol mixture. (2) On alumina. A special column was prepared to obviate "coning" because of the detailed separation which was required. Just above the 1 X 40 cm. column to contain the 100-200 mesh Alcan alumina (activated a t 150' for 24 hr.) was concentrically sealed a tube of slightly larger diameter. A glass rod of 2.5-mm. diameter was then equipped with trigonally arranged spacers to fit the bottom and top of the enlargement and to allow the bare glass rod to extend halfway down (20 cm.) and in the center of the tube which subsequently was filled to a depth of 40 cm. with the alumina suspended in hexane. The eluate (in petroleum ether solution) freed from hydrazobenzene by the silicic acid column was subsequently separated on these alumina columns. The substances, if they were present, appeared in the following order: diphenylethane, sym-di-n-propylhydrazobenzene, sym-dimethylhydraaobenaene, N-isopropylhydraaobenaene, N-methylhydraaobenzene, hydrazobenzene. Scission of b,6-diozahezane. A solution of 0.0095 mole of azobenzene-disodium adduct in 40 ml. of dioxahexane was shaken a t 20-25' 55 days and then treated with 2.60 g. (0.021 mole) of dimethyl sulfate a t 0-5". The crude product (2.064 g.) was isolated by ether extraction leaving an aqueous phase that contained 439 mg. of sodium ion (calcd. for 0.01 mole of adduct, 460 mg.). Chromatogra,phy on silica gel gave 0.03 g. (5'30) of hydrazobenzene. Separation of the remainder on alumina yielded 1.03 g. (49%) of N,M'-dimethylhydrazobenzene (XVI) and 0.524 g. (26%) of N methylhydrazobenzene (XV). Eeaction with dimethvl sulfate. A solution of 2.60 g. (0.021 mole) of dimethyl sulfate in 5 ml. of dioxahexane was added dropwise to 0.01 mole of azobenzene-disodium addurt a t 0-5". The color changed from deep red to light orange a t the end of addition, and then to light yellow when the system was warmed to 20". The residue after solvent evaporation was treated with 5 ml. of IN aqueous sodium hydroxide for 12 hr. The system was extracted with ether to remove 2.12 g. of crude product which was dissolved in hot methanol. The solution, cooled to O", precipitated an oil xvhich crystallized on further cooling. The methanol was decanted a t 0" and the magma rvas redissolved in hot methanol; cooling yielded 0.43 g., m.p. 32.5-33'. The evaporat,ed filtrates left a residue which was dissolved in petroleum ether and then applied to an alumina column. A further 1.53 g. of Y,I\"-dimethyIhydrazobenzene, m.p. 32.5-33.0", was obtained. Total yield was 92% of the theoretical. A similar experiment with the dilithium adduct gave a 9GYflyield. Reaction with n-propyl chloride. The disodium adduct (0.01 mole) was treated with 1.73 g. (0.022 mole) of n-propyl chloride, b.p. 46.5". Reaction was completed in 5.5 hr. The crude product, 2.479 g., crystallized from 20 ml. hot methanol, gave 1.47 g. of yellow crystals, m.p. 70-71'. The evaporated mother liquor, chromatographed on alumina yielded 0.818 g. more of N,iV'-di-n-propylhydraaobenzene, Crystallization from hot methanol gave 1.976 g. (747,), m.p. 71.5-72
'.
380
REESOR AND WRIGHT
VOL.
22
Anal. Calcd. for ClsH2rN2: C, 80.7; H , 8.96; K, 10.4. purified by repeated ( 5 times) crystallization from methanol Found: C, 80.7; H, 8.98; K, 10.3. (10 ml./g.) a t 0". Reaction with benzyl chloride. Azobenzene-dipotassium Anal. Calcd. for C18HZ,K2:C, 80.6; H, 8.96; K, 10.4. adduct (0.01 mole) was treated with 2.78 g. (0.022 mole) Found: C, 80.3; H, 8.95; N, 10.4. of benzyl chloride, b.p. 63" (8 mm.). Much heat was evolved The x-ray diffraction pattern was: [lo] 4.247; [9] 3.751: and an addition time of 35 min. was needed to hold the tem[SI 8.75; [ 7 ] 11.18, 7.02; [6] 5.71; 151 5.50; [4] 3.035, 2.928. perature t o 5" by means of an ice-water bath. The resulting Reaction with triisopropyl phosphate. Azobenzene-dipotasblue system became yellow-orange after five hours a t 25". sium adduct (0.01 mole) was treated with 4.93 g. (0.022 The crude product, 3.58 g. from the ether extract, was mole) of triisopropyl phosphate, b.p. 78-79' (2-3 mm.), n'," thrice extracted with 5-ml. portions of boiling petroleum 1.4057, d y 0.986. The reaction was very slow and is not ether leaving 2.54 g. (70ye,)of N,N'-dibenzylhydrazobenrecommended as a source of AV-isopropylhydrazobenzene. zene, m.p. 123-124". Three crystallizations from ethyl ether isopropyl methanesulfonate (by R. Kullnig). Following the (20 mi. per 9.) gave 0.50 g., m.p. 1.26.5-127.0". prescribed method13 30 g. (0.5 mole) of 2-propanol (purified R?zaE. Calcd. for CzsHSaS2:C, 85.7; H, 6.59; N, 7.69. by distillation after an hour reflux over aluminum isoproFound: C, 85.4; H, 6.73; iv, 7.50. poxide) was mixed with 50 ml. of barium oxide-dried pyriThe x-ray diffraction pattern was: [lo] 4.87; [9] 4.29; [SI dine. T o the solution a t 115' was added dropwise 63 g. 3.24; 171 3.83; [6] 7.69; [ 5 ] 3.53; [4] 7.96,7.43. The petroleum (0.58 mole) of methanesulfonpl chloride in 20 ml. of pyridine ether extract was chromatographed on alumina by means cooled to -15". dddit,ion of the cold solution required 20 of petroleum ether to give 151 mg. of diphenylethane, m.p. min. under strict exclusion of water. After 1 hr. a t -10' 51-52' (8%)) 193 mg. of azobenzene, m.p. 65-66' ( 7 % ) , and overnight a t +I' tho system was treated slow-ly with 159 mg. of dibenzylhydrazobenzene, m.p. 123-124" (4yo) about 50 g. of cracked ice and 100 ml. of 2 Y sulfuric acid and 25 mg. of N-benzylhydrazobenzene, m.p. 71-72' (1%). to dissolve crude salts. The crude product was separated by Iinown products were identified by mixture melting point. 4 extractions with 40-ml. portions of chloroform. The exMore of the moaohenzylhydrRxobenzene, m.p. 50-61 ', was tract combination, washed twice with 40 ml. of cold 211; obtained from the column by benzene elution. It was crys- sulfuric acid, 20 ml. of ice cold water, thrice with 20 ml. per time of saturated aqueous sodium bicarbonate, then four tallized from petroleum ether (10 mi. per g.) a t 0". Anal. Calcd. for ClsHlaK-:!:C, 83.2; H, 6.57; E,10.2. times with ice cold water. The cold nonaqueous phase was then dried overnight by magnesium sulfate. The solvent was Found: C, 82.8; H, 6.76; iv, 9.9. ;V,N'-Uiphenylpyrazol~dine. hzobenzene-disodium adduct removed in vacuo, finally a t 0.35 mm. The chloroform-free (0.01 mole) was treated with 1.20 g. (0.011 mole) of 1,3- residue was molecularly distilled a t 30" (0.02 mm.) to yield 59 g. (85%) of ester, dzo 1.145, ny 1.41'73, m.p. 5.5-8.5". dichloropropane, b.p. 125', in 5 ml. of dioxahexane a t 0-5". Anal. Calcd. for C,H,&3: C, 34.7; H, 7.29. Found: C, Evolution of heat mas apparent during the 70-min. reaction period. The crude product (2.19 g.) n a s crystallized from S4.4; H, 7.23. For characterization the ester (1.1 g., 0.008 mole) and ethanol, 1.23 g., m.p. 96-98', The mother liquor war evaporated in vacuo and dissolved in 3 ml. of petroleum 2-naphthol (1 g., 0.007 mole) in 3 ml. of acetone were refluxed m-ith 1.5 g. (0.0014 mole) of anhydrous sodium carether (b.p. 60-70'). This solution mas chromatographed on alumina to yield 87 mg. ( 5 % ) of azobenzene and 0.33 g. bonate for 2 hr. The solid was filtered off and the filtrate evaporated. The residue was heated 1 hr. with 5 ml. of more of the N,iV'-diphenylpyrazolidine (total yield 70%). ~~-,~~~'-Diphenylpyridazol.idine. To 0.01 mole of azobenzene- 20y0 aqueous sodium hydroxide in 3 ml. of ethanol. The disodium adduct was added at 0-5" a solution of 1.30 g. system was taken up in ether and the solution was washed (0.01 mole) of 1,sl-dichlorobiitane. Reaction was complete with water, dried with magnesium sulfate, and evaporated. in 4.5 hr. The crude product (2.55 g.) was dissolved in 50 ml. Crystallization of the residue from ethanol gave Z-isopropylof methanol; cryst,als appeared a t 0". A second cryst,alliza- 2-naphthyl ether, m.p. 40-41 ".I1 N,N'-Diisopropylhydrmobenzene. Azobenxene-disodium tion from 20 ml. of methanol gave 2.08 g. (85%) of diphenylpyridanolidine, m.p. 105.5-106". Two more crystallizations adduct (0.01 mole) was treated in the usual manner with 3.04 g. (0.022 mole) of isopropyl methanesulfonate. The (10 ml. per g.) raised the nielt'irig point' to 106.4-106.9". products were separated by the successive eluttion from Anal. Calcd. for CIGH&*: 6,80.7; H,7.53; N, 11.8. alumina by petroleum ether. I n this way a yield of 0.53 g. Found: C, 80.8; H,7.49; K>11.9. (20%) of diisopropylhydrazobenzene was obtained in addiThe x-ray diffraction patt,ern was: [lo] 4.168; [9]5.86; tion to a 66Ye yield of monoisopropylhydrazobenzene. [SI 5.211; I71 6.55; [6] 8.42, 2.93; [ 5 ] 3.437, 3.118; [4] Reaction with tert-butul chloride. Azobenzene-disodium 4.41,3.897. adduct (0.01 mole) was treated with 1.95 g. (0.021 mole) of The liquors from the first and second crystallizations were 2-chloro-2-methylpropane, b.p. 51 ', during 50 hr. The combined, vacuum-evaporated, and steam-distilled to yield crude product (2.34 g.) was dissolved in 4 ml. of petroleum 71 my. (4yo) of azobenzene in the distillate and 127 mg. ether and chromatographed on alumina. The eluate yielded (
